The compiler does not know how to convert those into Strings or cStrings, so you need to do this yourself. You use a 64 bits (8 bytes) long integer. When you do something like uint64_t espChipID = ESP.getEfuseMac() I won’t comment on the use of the String class, you know the pitfalls. What is clientHTTPMagicMirror? which library is being used? is there a way to post params independently? what is postAttributeFirmware, firmwareCode etc ? They are likely Strings indeed ut don’t post snippets ( Snippets R Us!) I found one possible lead with this code ( ) but I don't understand it well enough to know how to adjust it to input ESP.getEfuseMac() and get out a string called efuseMac.Īny help or pointers in the right direction would be appreciated. Unless someone can suggest another workaround, I think I need efuseMac and wifiMac to be strings as well. I'm no expert, but I believe this is concatenating a bunch of string to form the post. String payloadMagicMirror = clientHTTPMagicMirror.getString() The code for sending the data is: int returnCodeMagicMirror = clientHTTPMagicMirror.POST( postAttributeFirmware + firmwareCode + postAttributeEfuseMac + efuseMac + postAttributeWiFiMac + wifiMac + postAttributeSensorID + sensorID + postEnd ) My Arduino (technically an ESP32) sends some json data to my MagicMirror using HTTP POST. I'm pretty sure that someone is going to say, 'Why are you doing this? You shouldn't use a string.' So here's my situation: My basic question is how can I convert the units MAC address (from ESP.getEfuseMac() and/or WiFi.macAddress() ) into a string?

Convert mac address from hexadecimal